1. Field of the Invention.
This invention relates generally to mechanisms for guiding the travel of vertically propelled weights, such as a seismic gas exploder of the type which applies a downwardly directed impulse to the earth and which thereafter rebounds upwardly. The invention is especially concerned with mechanisms of this type designed to guide the travel of a seismic gas exploder along resilient ropes wherein the effect of eccentric or non-vertical motion of the exploder is minimized.
2. Description of the Prior Art.
As described in Applicant's co-pending application, Ser. No. 427,929, filed Dec. 26, l973, now U.S. Pat. No. 3,951,229, a seismic gas exploder may be positioned within a platform-mounted upstanding frame having supported therein from top to bottom a plurality of parallel tensioned ropes spaced in symmetrical array outwardly of the periphery of the gas exploder. The ropes are slidably engaged by bushings fixed to the extremities of a plurality of radially extending arms carried by the gas exploder so as to permit travel along the ropes in a vertical direction with elastic lateral support subsequent to an explosion.
An exploder guided as described above may be tilted and thrust upward at an angle to the vertical for several reasons, such as being positioned on uneven terrain or because the force of the initial explosion therein is not centered in a downward direction. In such case, if the encircling bushings are longitudinally short in relation to their bore diameters, the exploder can tilt considerably without forcing the ropes out of line. This increases the likelihood that one or more bushings will momentarily catch on their respective ropes, with the result that the exploder may pivot or swing about these points of contact with pendulum movement. This also increases the likelihood that the rope will kink or abrade.
Further, a single bushing or other interconnecting means with a short axis concentrates side loads against a rope or ropes over a short distance so as to increase the chance of rope failure under repeated use.
In order to improve the operation of this apparatus, the Applicant first considered lengthening the rope encircling bushings into long continuous sleeves so as to prevent the exploder from tilting against the ropes and to distribute the load more widely. This construction has the disadvantage, however, that a greater surface becomes available to create friction resistance to exploder movement. A solution was arrived at which has the advantages of a long sleeve and yet minimizes frictional resistance to such movement.
It is therefore a general object of this invention to provide an apparatus for guiding the travel of a seismic gas exploder of the type described wherein eccentric reactive forces transmitted by the exploder to the members defining its desired path are distributed so as to avoid high load concentration on such members.
It is another object of this invention to provide apparatus of the type described wherein the exploder is prevented from tilting substantially in relation to the path-defining members. It is a further object of this invention to provide an apparatus of the character described wherein the exploder is guided upwardly with a minimum of friction. These and other objects of this invention will become apparent from the following detailed description of the preferred embodiments of this invention and as illustrated in the drawings appended hereto.